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SESSION I (contd.)


Kazimierz Szebiotko
University of Agriculture
Institute of Food Technology of Plant Origin
Poznan, Wojska Polskiego 31 Poland


Methods should be elaborated and introduced in agricultural practice for preparation and preservation of by-products produced on farm, e.g. ensiling of feed components (straw, green plants and others). This very effective method is not in use in many African and other countries. Silage is always better utilized by animals than straw or hay.
For slaughter-house or fish processing where only small amounts of by-products are obtained, chemical acidification methods (sulphuric acid 1–1.5 kg/100 kg by-products or hydrochloric acid 0.2 kg and 2 kg of formic acid/100 kg) can be used. Such a product can be added to swine feed in amounts of 1 kg per head daily.
Utilization of protein and vitamins from green biomass of plants in mongastric animal nutrition will play a very important role in improving the economic utilization of agricultural products. The proposed method is very simple and effective and can be introduced even in very small farms. This method is based on the separation of leaves from stems. In the leaf fraction we obtain high concentration of protein and vitamins (about 200% higher than in the whole plant). The stem fraction has a lower content of protein but very high amounts of fibre. In alfalfa leaf fraction the content of protein varies from 27 to 32% and of fibre 12–13%; from carotene 120–150 mg%. This method is very effective for plants like alfalfa, clover, lupins, vicia faba etc. Sun dried material after crushing can be separated by using sieves or forced air. This technique, due to the easy application and energy conservation, may be used on large scale farms.
In ruminant and monogastric animal feeding, appropriate mineral or mineral-vitamin concentrates should be added to the feed produced on the farm. In this case, extensive research on composition and nutritional value of grasses and other feedstuffs in various regions of Ethiopia and other countries should be carried out to establish the composition of such concentrates.
Ammonia, either in aqueous or anhydrous form, can be used for removal and inactivation of toxic substances produced by different fungi. Ammonia detoxifies aflatoxins. Ammonia is also very useful to preserve wet grain and other plant seeds used as feed. The amount of ammonia added to grain or other products to prevent spoilage depends on the moisture content and ranges from 1 to 3.5% for H2O content of 17–32%. This method can be applied for long or short term grain storage.


The increase in human population in Europe over the last decades has influenced greatly the demand for food products of animal origin. In consequence this requires a considerable development of animal production. The main interest in this paper is focused on the monogastric animal, mainly swine and poultry.

According to literature and everyday breeding practice, the monogastric animals, apart from their high rate of reproduction, are characterized by the best efficiency of nutrient transformation into high-quality animal protein. Nevertheless, the costs of this transformation are very high. Feed conversion expressed in kilogrammes of feed per kilogramme of body weight gain ranges from 2.0 to 2.8 and from 3.5 to 4.5 in broilers and pigs, respectively. This indicates that from 4.5 to 6.0 kg of plant protein is converted into one kilogramme of animal protein only.

Several factors like breed, genetic selection, age, management conditions, properly balanced feed mixtures and primarily, the quality and amount of protein in relation to energy/net energy, influence the amounts of protein and energy used by the animals for 1 kg weight gain. So we can say that protein and energy resources are the fundamental factors limiting the size of animal production in each country and region of the world.

The feed situation in Europe indicates that to maintain the population of animals at the present level, the protein deficit is of the order of 25 to 28 million tonnes and varies from several hundred thousand to several million tonnes in various countries. For instance, Denmark with its developed agriculture and high animal production, imports 30% of the total amount of utilized protein to cover the country's protein demand. About 2/3 of the imported feedstuffs consists of oilseed meals and animal origin meals; the rest is grain and cereal products. In Poland the estimated protein deficiency is 1.5 to 1.8 million tonnes, which is 17% in relation to the amount of protein consumed as fodder.

This situation forces the European countries to import high-protein feed components mainly in the form of oilseeds, oilseed meals, animal origin meals and grain and also to utilize all of the available raw materials and wastes in the best possible way for feed production. Food industry by-products and crop residues are used as components of commercial feed mixtures or added to feeds prepared directly on the farms.

Food industry by-products and agricultural wastes used in feeding of monogastric animals can be divided into three main groups:

The animal by-products originate in the slaughter-houses of large animals and poultry and on fish-processing ships and comprise such products as: meat and bone offals, blood, bones, intestines, poultry heads and feet, fat, feathers, bowels, horns, hooves, animal hair, stomach, intestine and rumen content, and the carcasses of animals disqualified by the veterinary service. To this group should also be added dairy industry by-products not utilized for food production (cheese, whey, casein, butter-milk) as well as tannery by-products. Animal and poultry manure which is currently used as a feed ingredient can be included in this group.

By-products of plant origin consist of:

By-products of the fermentation industry include grain, molasses, potato distillers’ solubles, brewer's and wine yeast, bacteria and fungi biomass as a waste from production of lactic and citric and other organic acids, as well as spent grain and malt sprouts in breweries. Activated sludge from waste water treatment plants in the food processing industry is also used.

A separate group of by-products is represented by those collected in big urban centres, e.g. kitchen wastes especially coming from large catering establishments, which after suitable steaming and ensiling are added to swine feed.

In the by-products mentioned above the following characteristics are most important: protein concentration and its biological value, quantitative and qualitative composition of amino acids, digestibility, level of energy, fats and carbohydrates, vitamin and mineral content; and the amount of fibre and substances that might be hazardous or toxic to the organism. The quantity of by-products used as feed depends on the country's resources and the techical equipment used for its preparation, preservation and improvement. However, in many countries there is a tendency towards a maximum utilization of all products which are suitable for feed purposes. This is followed by elaboration of suitable methods of collection, transportation and processing aimed at reducing costs and improving the nutritive value.

Methods and means of by-product preparation for feed

Considering the properties and chemical constitution of by-products and wastes, various techniques are used for:

The following techniques are most often used in the preparation of by-products for feed purposes.

Autoclaving under pressure at 115° – 140°C followed by drying and removal of fat by pressing or extraction. This technique is commonly used to obtain various kinds of animal protein meals such as: meat and bone; poultry, fish, feather, and other meals produced from dead and condemned animals. Meals obtained in this way are under rigorous sanitary and microbiological inspection and are subjected to biological tests to detect the presence of pathogenic bacteria and toxic constituents.

Hydro-thermal, acidic and alkali hydrolyses are used for proccessing waste rich in keratin, e.g. feathers, hooves, animal's hair, tannery wastes, or some plant products containing glucosides, such as rape meal. Hydrolysis of keratin is performed by a hydrothermal process at 135°–150°C, followed by drying. In some countries acidic or alkali hydrolysis is replacing the thermal method.

Mechanical or thermal condensation and drying-toasting. Centrifugation, pressing or condensation in a vacuum evaporator is followed by spray, roller, flash or drum drying. These techniques are used for preparation of dehydrated milk products, yeasts, grain, potatoes, molasses, distiller’ solubles, brewery waste, solvent-extracted meals from oilseed and also blood of slaughtered animals.

Microbiological and chemical souring. These techniques are used to preserve the by-products and are an effective method of removing harmful substances e.g. VTO, isothiocyanates from rape, souring of skim milk and whey, preserving by-products of animal origin, blood, rumen content and animal and poultry excrements which are now used as a fodder ingredient. These techniques, because of their easy application and energy conservation, are used on a large scale on all farms. A very important attribute of souring, besides preservation, is the possibility of product deodorization, which is difficult to achieve in other processing techniques.

Souring of whey, skim milk, spent wash and wastes of the brewery and sugar industries has been used for years. It is a very economic and effective method of preservation and protection of feed against spoilage. For instance, in Denmark, skim milk is first soured in a dairy by using lactic acid bacteria for 24 h and then it is added to pig feed on the farm. Research carried out in the last few years proved that souring of rapeseed meal can completely remove goitrogenic substances (VTO and isothiocyanates). The presence of these substances is a limiting factor in using rapeseed meal in pig and poultry nutrition.

Chemical acidification can be used instead of drying when suitable equipment is not available to process fish wastes and inedible fish. For 100 kg of comminuted product, 0.2 kg of concentrated sulphuric acid, 0.2 kg of hydrochloric and 2.0 – 2.5 kg of 80% formic acid are added. Hydrolysis-autolysis process is performed at 25°–35°C. In the second method, 0.7% sulphuric acid and 1% of sodium pyrosulphite are added to 100 kg of comminuted product (pH about 3.9). Protein content in these hydrolysates varies from 12 to 15%. They can be added to swine feed in amounts of 1 kg per head daily. This amount provides about 30% of the protein requirement and can be condensed or dried together with other feed products if necessary. The same process can be applied to blood and other by-products. For 100 kg, 1.0 to 1.5 kg of sulphuric acid and 0.2 kg sodium pyrosulphite is added.

Selected chemicals and techniques should be used to inactivate or to remove toxic metabolites produced by fungi, e.g. aflatoxins, ochratoxins, zearalenones, trichotecenes, penicilic acid and some others present in grain products, oilseeds and legumes. These metabolites not only decrease the nutritive value of feed components, but can also cause serious diseases or even death of animals.

Microbiological biosynthesis of SCP, enzymes, aminoacids, vitamins such as B12c. In this method, whey, molasses, hydrolyzed beet pulp and other products containing carbohydrates or cellulose and the non-conventional sources (n-parafins, methane, methanol) are fermented using various strains of yeasts, fungi and bacteria. There is much prospect for these processes in solving world feed problems.

The processing technique necessary to convert a great number of by-products into monogastric animal feed must be selected in such a way as to reduce to a minimum the quantitative and qualitative losses of nutrients. Extensive research carried out in various countries for decades on the production of animal origin meals resulted in elaboration of optimum temperatures for sterilization and drying. These parameters reduced by 10 times the losses of essential amino acids especially lysine, methionine, cystine, tryptophan and others and improved the digestibility of protein. Progress in this area concerned first of all the reduction of sterilization temperature and time and their detrimental effect on the product. The temperatures vary from 120° to 130°C and time from few to a dozen minutes, according to the nature of the raw material. For instance, in the Soviet Union the slaughter wastes are cooked to kill the microorganisms and then dried in a thin layer at 85° – 95°C. This results in a very high biological value of protein and high vitamin content.

The second resolved problem is simultaneous processing of poultry offals instead of using separate ones for feathers, blood and other products. This technique is better for economic reasons and feeding results do not differ from those with meals obtained by separate processing or with fish meal.

Considerable research was also devoted to the utilization of keratin products such as feathers, animal's hair (from cattle and hogs), hooves, horns and others.

Hydro-thermic hydrolysis is very effective but more expensive than acid or alkali hydrolysis. The meals obtained can be used as feed components for chickens, ducklings, geese and for animals in amounts from 2 to 6% of total feed. Meals produced from tannery wastes and containing mainly collagen proteins might replace in pig rations up to 18% of plant protein.

According to numerous authors and data obtained from commercial practice, various techniques are used in processing by-products and wastes for feed depending on type and quality of the produced feed components and kind of animal. However, the main purpose of adding by-products to feed is not only to raise the protein and energy content, but also to elevate the biological value of feed through its supplementation with essential amino acids, B-vitamins of yeasts; vitamin B12 of bacteria and fungi biomass, and with numerous other unidentified growth factors. So the quantity and the kind of a particular product added directly to the ration or feed formula is diversified. This is illustrated by the data which are presented in a condensed form.

TABLE 1 The amount of by-products used in swine feed in % without the grain and vitamin-mineral components
ItemFeed for
sowyoung pigpighog
Wheat bran35.015.015.0-
Rye bran------10.0
Fish meal7.
Blood meal----2.0--
Soybean meal8.015.04.0--
Peanut oil meal----9.08.0
Rapeseed meal------3.0
Cottonseed meal------3.0
Yeast dried1.5--2.02.0
Alfalfa meal4.
Skim milk/dried/--7.0----
TABLE 2 The amount of by-products used in poultry and other monogastric animals in % without the grain and vitamin-mineral component
ItemFeed for
Blood meal3.0--------
Fish meal6.
Meat and bone scrap--
Rapeseed meal3.0--------
Soybean meal-
Peanut oil meal12.0--------
Yeast dried2.
Barley malt root4.0------5.0
Skim milk /dried/--3.02.0----
Alfalfa meal4.0----4.026.0
Wheat bran--------15.0

The examples presented indicate that the feed ingredients are used in various quantities and range from several to a dozen percent. In particular countries the amounts of processed by-products used in poultry, swine, rabbit, horse and fish feed vary considerably.

Feed quality is assessed not only on the basis of the protein and metabolizable and net energy content; in many countries the level of amino acids, primarily lysine and methionine, is used as the quality criterion.

Regarding the utilization of food industry by-products and agricultural wastes two points should be taken into consideration.

In solving the problem of by-product utilization in monogastric feeding, a very important role is played by scientific research which has contributed greatly to the progress made in Europe over the last decade. However, it is indispensable to continue research activity in many areas, namely:

  1. To elaborate simple techniques of waste utilization to decrease losses in the nutritional components; to improve digestibility and availability of the finished products and to lower production and preservation costs.

  2. To elaborate simple methods of waste preservation and preparation, to be used directly on the farm, e.g. souring in biological or chemical ways.

  3. To work out methods of removal and inactivation of harmful substances, such as: alkaloids, glucosides and other anti-nutritional and toxic substances produced by fungi-mycotoxins, which can be present in plant products.

  4. To continue research on the utilization of indigestible feed components in animal excrements.

  5. To continue research on the utilization of cellulose-rich plant wastes for monogastric species, using microbiological techniques.

  6. To carry out extensive physiological and nutritional research on the optimum doses of processed wastes for each kind of animal, in relation to their needs, age, genetic character, quantity and quality of other feed components.



Ruby T Fomunyam
Institute of Animal Research
Mankon - Cameroon


Several tonnes of agro-industrial by-products are produced each day in Cameroon. Although there is variability in the chemical composition, the costs of the products as well as the costs of processing them, there exists a great potential for producing good quality meat from these feed items within the operational limits of the small-scale farmer in Cameroon. This would greatly reduce competition with man for feed resources. Cottonseed meal, the major protein source in Cameroon, has promoted efficient growth when fed to non-ruminants and ruminants. Chicks fed test diets in which 0, 50, 75 and 100% soybean was replaced by cottonseed meal in corn-soybean diets had similar growth rates. In swine diets, 14, 20 and 45% rice bran fed in place of corn were found to be optimum levels for suckling, grower and finisher pigs. Carcass traits showed that more lean meat and profit were realised from market pigs as the level of rice bran increased in the diets, suggesting that grading pork prior to sales would greatly encourage the production of better quality meat in Cameroon.


Cameroon, a land of about 475 000 square kilometres, like most African nations, does not have a grain surplus but is basically an agricultural country and consequently produces many agro-industrial by-products. With an estimated 2.4% annual population growth rate, more meat, milk and eggs must be produced. This must be done with minimal competition between humans and animals for feed resources and at costs which will enable competition with, and/or to prevent, imports while encouraging exports. The Cameroonian farming population is made up predominantly of small scale farmers with the exception of a few private and state-owned large scale farms. The agro-industrial technological package must be tailored to the level of the small farmer. In Cameroon, a great need exists to reduce animal weight loss usually observed in the dry season and to maximize meat production from feed sources not utilized by man, such as agro-industrial by-products.


The estimated quantities of agricultural residues usually left on the farm after harvest are shown in Table 1. These by-products are obtained free on the farms and so their costs comprise mainly the time and labour used to locate, collect and transport them from farms to feeding centres. Yet, little has been done to maximize the exploitation of these by-products as potential feed sources for livestock production. Sheep, goats, pigs and poultry are let loose shortly after harvest and share these residues with pests and birds in the field. What is not eaten up is quickly baked dry by some twelve to fourteen hours each day of the dry season sun and is ploughed in at the start of the rains or, runs the risk of bush fires. Waste bananas in excess of exports are consumed locally and the rest left to rot. There is an accelerating programme to increase upland and paddy rice and cassava production; thus there will be an increase in the by-products of these crops.

The convenience of bagging and collection at a particular location of the second group of by-products (Table 2) is reflected in the slightly higher costs of these. Cottonseed meal is produced in the northern part of Cameroon and trucked to the rest of the country. Groundnut meal was produced similarly, but production stopped two years ago. Palm kernel meal, the only other major protein source, is produced from the oil mills in the south of the country and trucked to other parts, although about half of the palm kernels produced are exported. Table 3 shows the chemical composition of some of these by-products. There is great variability in the factory by-products, suggesting a need for greater control in the bagging so as to enable uniform feed mixtures to be prepared. The crude protein of Cameroon cottonseed meal averages 49% compared to values of 41% usually recorded for this product. The gossypol content varies from 0.02 to 0.04% (free gossypol), while the crude protein content of Palm Kernel meal is about 15.2%.

TABLE 1 Farm Residue - Agricultural By-Products
MAJOR CROP ('000 tonnes)RESIDUE (`000 tonnes)% Extraction rateCost : FCFA per kg *CURRENT USE (Animal species)
Corn (500)Waste Corn (25)530Chicken, pigs, rabbits
sheep, goats, cattle
Sheep, goats, cattle
Corn Stover (000)20025
Rice (129)Broken Rice (12.9)1045Poultry, Sheep, Goats
Rice Straw (129)10025Sheep, goats, cattle
Groundnuts (150)Haulms (86)5710Rabbits, goats
Shells (45)4030-
Cassava (620)Tops (620)10028Sheep, goats, cattle,
Rabbits, goats, sheep
Peels (50)825
Bananas (100)Waste Banana (300)308.0Pigs
Cattle, rabbits, goats
Stems/Leaves (60)100100
Sweet Potato (70)Sweet Potato  Rabbits,goats
Cocoa (139)Husks (97)7017Rabbits, cattle
Waste Bean (14)1014Pigs

* 400 FCFA = US$ 1

TABLE 2 Agro-Industrial By-Products (Processing Plant Residue)
RESIDUEQuantity ('000 tonnes)% extraction rateCost:FCFA per kgCurrent use (animal species)
Maize Bran801635Pigs
Rice Bran131060Pigs, Poultry, Rabbits, Sheep, Goats, Cattle
Rice Polishings191565Sheep, Goats
Brewer's Wet Grains33108.05All species
Coffee Pulp8010015Pigs
Cottonseed Meal161870All species
Palm Kernel Shells125100--Fuel
Palm Kernel Meal252040All species
Palm Press fibre125100--Fuel
Palm Oil Sludge3225--Fuel
Soya Bean meal*.5201400 

* Imported; production quite low in Cameroon

TABLE 3 Chemical Composition of By-Products (%)
Cottonseed Meal94.844.16.611.024.9
Palm Kernel Meal94.
Rice Bran92.08.216.612.08.4
Groundnut Haulms94.914.69.320.02.0
Sweet Potato Leaves93.624.112.315.03.8
Rumen Contents91.011.112.430.01.4
Brewer's Dried Grains91.826.
Coffee Pulps65.010.810.220.02.7
Banana Leaves94.


About eighty per cent of meat production is attributed to feeding of animals. Corn is more expensive when compared to crop residues in Cameroon and the quantities of rice and sorghum are not adequate for the population, thus their use for animal feed is out of the question.

Pigs and Poultry

Feed costs and animal competition with humans for feed items suggest strongly that alternative energy sources such as residues of crop harvests be used partially or totally to replace maize in livestock diets, reducing cost, and enabling cheaper meat production and making available major crops for human consumption. In poultry production, cottonseed meal fed at 0, 6.2, 12.5, 18.7 and 25% respectively in a corn-based diet to replace 0, 25, 50, 75 and 100% soybean meal revealed no significant changes in terms of feed intake, growth and feed conversion (Ngou and Mafeni 1983). Soybean meal costs 1 400 FCFA/kg while cottonseed meal costs 70 FCFA/kg. In swine diets, 24, 10 and 14% levels of cottonseed meal have been used in suckling, grower and finisher/breeder diets without any deleterious effect. Dwarf forest sheep and goats and cattle fed a cottonseed meal supplement showed no reduced weight losses normally observed in the dry season (Ndamukong 1983). Although cottonseed meal shows a great potential as a cheap protein, non-production of groundnut meal due to technical problems emphasizes the need to investigate other sources of protein such as rubber meal, copra meal and fish meal.

Rice Bran0.
Cottonseed Cake24.524.524.524.510.
Brewer's Dried Grains--------------
Palm Kernel Cake5.
Palm Oil3.
Fish Meal5.
Blood Meal--------6.956.956.95--------
Bone Meal0.750.750.750.751.
Vitamin/Mineral Premix0.750.750.750.750.

Swine were fed rice bran in suckling, grower and finisher diets (Table 4). The results (Fomunyam R, Unpublished) showed that growth rate of pigs fed test diets were similar. Levels of rice bran up to 20% were found appropriate for growing pigs while finisher pigs utilized 45% levels of rice bran efficiently. Analyses of the costs showed that grading swine meat would be beneficial and would encourage production of cheaper and better quality meat.


The rabbit has good potential to extract protein from plant material. A 4 kg doe has the ability to produce 84 kg of meat per year. Rabbits fed 10, 20, 30,40 and 50% respectively of fresh groundnut haulms in place of corn/cottonseed meal, ate 101, 113, 115, 120 and 127 g/day respectively and gained 13, 19, 18, 18 and 17 g/day. In a related study, field dried groundnut haulms were not well utilized by rabbits. Weight gains of 15, 15, 13, 11 and 10 g/day were observed for the levels of 10, 20, 30, 40 and 50% of pasture dried groundnut leaves in the diets. In another study, weaning rabbits were fed 30 % fresh banana/plantain leaves, a mixture of 15% fresh and 15% dried leaves and 30% sundried leaves in place of corn. Feed intake was 67, 33 and 44 g/day and weight gains were 20, 19 and 20 g/day. Thus eight kits weaned from a doe at three weeks of age weighing 500 g each can produce 5 kg of meat in five weeks time when fed these crop residues. The small scale farmer and family can thus increase their protein consumption as well as sell the excess meat.


Zebu cattle initially weighing about 267 kg were fed test diets in which rice bran replaced 0, 50, 75 and 100% maize in a beef fattening experiment (Ndumbe 1981). Dry matter intake was 6.7, 6.6, 7.3 and 5.6 kg/day while weight gains were 0.9, 1.0 and 0.5 kg/day respectively. It seems the 75% level of rice bran replacement of corn was better utilized than the other levels.

One of the major steps in the use of feedstuffs is to know its chemical composition and the efficiency of its utilization by animals (Gomez 1982). In Cameroon, the newly established National Feed Laboratory at Mankon, Bamenda will enable more investigations to be made into the lesser known but utilizable by-products such as bean stalks, tea plant by-products, groundnut shells and fruit plant by-products, etc.


The slow growth rate of livestock when fed by-products suggests poor feed intake and poor digestibility. Several processing methods have been suggested, (Sundstol, Coxworth and Mowat 1978; Said 1981 and Kategile 1982). However, chemicals are expensive and must be imported at least six months to a year in advance and are hazardous. Thus the technology of processing must be carefully costed and programmed to fit within the income and competence limits of the Cameroonian farmer.

Feed analysis is becoming very expensive in terms of reagents, infrastructure, energy and equipment repairs. Simple, cheap basic analytical procedures must be sought to give the needed research data.

Although there are large quantities of by-products, the collection and transportation of these from small farms dotted here and there is a tedious, time-consuming affair. There is also great variability in these products from farm to farm as the planting and harvesting of crops is not synchronised. However, these constraints are challenges in the process of obtaining meat from the vast amounts of agricultural by-products at little or no competition with man for feed items.


Gomez, M. 1982. Nutritional Characteristics of Some Selected Non-Conventional Feedstuffs: Their Acceptability, Improvement and Potential Use in Poultry Feeds; In “By-Product utilisation for Animal Production” Kiflewahid B., Potts G.R. and Drysdale R.M. ed., Nairobi, Kenya.

Kategile, J.A 1982. Utilisation of Low Quality Roughages with or without NaOH Treatment; In “By-Product Utilisation for Animal Production”, Kiflewahid B, Potts G.R. and Drysdale R.M. ed., Nairobi, Kenya.

Ndamukong, K.N. 1983. Supplementation of Cottonseed Cake for Maintenance of Sheep and Goats on Pasture in the Dry Season. Annual Report, Institute of Animal Research, Mankon, Cameroon, pp 34–36.

Ndumbe, D.R. 1981. The value of Rice and Maize By-Products in Beef Cattle Nutrition. Presented at the FAO/ILCA Work-shop on Utilisation of Agro-Industrial By-Products and Crop Residues in Animal Feeding, Dakar, Senegal, 21–25 September 1981.

Ngou, J.N. and Mafeni, J.M. 1983. The Value of Cottonseed Meal in Poultry Diets. Annual Report, Institute of Animal Research, Mankon, Cameroon, pp 34–36.

Said, A.N. 1981. Sodium Hydroxide and ammonia-Treated Maize Stover as a Roughage Supplement to Sheep and Beef Feedlot Cattle. In: Kategile, J.A. Said, A.N. and Sundstol, F. ed., Utilisation of Low Quality Roughages in Africa; AUN-Agricultural Development Report 1, Aas, Norway 107–112.

Sundstol, F., Coxworth, F. and Mowat, D.N. 1978. Improving the Nutritive Value of Straw and Other Low Quality Roughage by Treatment with Ammonia; World Animal Review 26, 13–21.


M G E1-Hag
Department of Animal Nutrition
Faculty of Agriculture
Shambat - Khartoum N Sudan

A survey indicated that over 4.5 million tonnes of agro-industrial by-products are available in Sudan. It is estimated that the energy present in these by-products could satisfy about 9% of the maintenance requirements of the animal population in the Sudan (about 55 million head of cattle, sheep, goats and camels). The major by-products include: cereal straws, groundnut hulls and haulms, sugar cane tops, bagasse, molasses, cotton stalks and trash, sesame field residues, wheat bran and cottonseed cakes, and field residues of sorghum and cotton after crop-harvest.

Laboratory analysis indicates that most by-products are of relatively poor quality with very high contents of lignin and crude fibre and low content of nitrogen.

Seven different feeding trials were conducted with cattle, sheep and goats. The rations contained cottonseed cake, wheat bran, molasses and urea with roughage supplied by cereal crop residues, or bagasse, or groundnut hulls. Animal performance was comparable with that obtained on conventional high grain rations but the cost was 50% less.

Different methods have been studied to enhance the nutritive value of groundnut hulls, sorghum straw and bagasse. Results were not very encouraging either for ensiling or NaOH treatment applied to groundnut hulls and sorghum straw. Based on these findings the use of NaOH is not advocated under Sudan conditions due to its high cost, lack of experience in its use and hazards encountered with its application.

The method which proved to be successful and promising was physical treatment (grinding and pelleting). Levels of pelleted bagasse of 30, 40 and 50% resulted in improved digestibility and intake of the overall diet with 40% better animal performance. This method is recommended under Sudan conditions because of its simplicity and cheapness compared to chemical treatment.


N Mbaye
Laboratoire National
d'Elevage et de Recherches Vétérinaires
Dakar Senegal

Since 1967, many studies have been carried out at the Institut Sénégalais de Recherches Agricoles (ISRA) on the availability and nutritive value of agro-industrial by-products and crop residues in Senegal.

Crop residues include: straws of rice, millet and sorghum and stover and cobs from maize; and the haulm from groundnuts and beans.

Agro-industrial by-products include shells/hulls from groundnuts and cotton; oilcakes of groundnut and cotton; and brewers' grains.

Research methodology is based on classical proximate analysis; the detergent fibre procedure; in vitro digestibility by enzymes and the “Tilley-Terry” technique, and intake, digestibility and growth studies with sheep.

The overall objectives are to determine the nutritive value of the feed resources, the animal requirements and feeding standards for different situations, and to predict animal performance from feeding trials.


A A Adegbola

University of Ife, Nigeria

Crop residue By-productEstimated quantityCurrent role in animal productionConstraints on useCost at source (in N/tonne) LocationTransportation
Molasses92 000Beef productionMainly fermented into alcohol30.0010.00
Bagasse483 000Rarely usedUse for fuel in factorynot costed
Cocoa pod600 000Use in ruminant feed experimentallyCollection, drying grinding. Lack of awareness by farmers 25.00
Cotton seedUnknownSupplement in ruminant diet. Limited used in swine feed.Not readily available for feed. Presence of gossypol. Low S-amino acid content.200.005.00
Cassava peel (from garri)Not yet estimatedTraditionally used in ruminant diet.Contains glucoside May require ensilingnot as yet
saw-dustNot yetExperimental use as rabbit feed in compound dietsRequires processing as silage with poultry manureNot of any value as yet
Brewers' grain25 000 in 1982Use for feed by dairy beef, sheep, goats. Also in paultry feed.Collection, drying bagging60.0010.00
Wheat offal400 000 in 1982Use in beef and poultry productionMainly exported to Europe80.0030.00
Rice branUnknownLow levels in started and grower diets. 30% for weaner pigs.Not readily available60.0010.00
Maize millings"Supplement for sheep and goats"None as yet
Maize stover"Dry season feed for cattle, sheep and goatsPoor integration farming systemUsually collected farm site by livestock
Millet straw""""
Groundnut haulms"Supplement feedto cattle and sheepNot readily available40.005.00


N A Urio

University of Dar es Salaam, Morogoro, Tanzania

STOVERS AND STRAWS (Figures for grain, Ministry of Agriculture/FAO Early Warning Project for 1984/85 Season)
CropEstimated production ('000 tonnes) of grainRatio of residue grainEstimated production ('000 tonnes) of stover strawCurrent use in Animal productionConstraints on use
Maize15492.03098Grazed and limited stall feeding around Kilimanjaro/ Arusha areasLow density collection and high transportation costs
Sorghum5543.72049Grazed in situ inefficientMethod of feeding
Paddy3791.0379NegligibleLow nitrogen content. lack of suitable methods of improvement
Millet3733.71380Grazed in situLack of suitable and efficient methods of collection and storage
Beans442--Small stall feeding to dairy cattle around Kilimanjaro/Arusha areasAs above

MILLING BY-PRODUCTS (Production figures Tropical Products Institute, London)
By-productsEstimated annual production ('000 tonnes)Current use in animal ProductionConstraints on use
Maize bran7.0Wholly utilized in ruminant and monogastric feeds-
Wheat bran14.5Used for dairy cattle feeds-
Wheat pollard9Wholly used for poultry and pigs-
Rice branUnknownLimited amounts used for ruminants-
Rice PolishingsUnknownUsed mainly for pigs and poultry feeds-
OILSEED CAKES (Marketing Development Bureau, Dar es Salaam)
CropEstimated production of oilseeds ('000 tones)Estimated production of oilseed cakes ('000 tonnes)Current use in animal productionConstraints on use
Cotton seed12340Utilized in ruminant and monogastric feedsAn appreciable quantity exported, despite the high local demand
Sunflower12Not knownUsed for poultry feeds-
Sesame6.5Not knownUsed wholly for poultry feeds-
SoybeansUnknown0.9Used wholly for mono- gastric feeds-
Copra2.0Not knownUsed for ruminant feeds-
By-productEstimated production ('000 tonnesCurrent use in animal productionConstraints on use
Molasses40About 4–5000 tonnes used in the livestock industry mainly Kiliman jaro/Arusha areaHigh transportation costs- Large quantities thrown away
Sisal waste700Limited to experimental testsLack of technology for separation, drying to reduce bulkiness and transportation costs

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